1. Field of the Invention
The present invention relates to a recording tape cartridge, particularly, a recording tape cartridge of which a single reel on which a recording tape such as a magnetic tape used as recording and playback medium for a computer or the like is wound is accommodated within a case.
2. Description of the Related Art
Conventionally, a magnetic tape cartridge, of which a single reel on which a magnetic tape used as data recording and playback medium for a computer or the like is wound is accommodated within a case, is known. A leader members such as a leader block, a leader pin and a leader tape are provided at a tip end of this magnetic tape. A drawing device, which is provided at a drive device, draws the leader members from the magnetic tape cartridge, and the magnetic tape fixed to the leader members is wound on a take up (a winding) reel of the drive device.
Recording of data onto the magnetic tape or playback of data recorded on the magnetic tape is carried out by synchronously rotating the reel of the magnetic tape cartridge and the winding reel of the drive device. The reel of the magnetic tape cartridge is structured such that a cylindrical hub and a lower flange which protrudes in a radial direction from a lower peripheral portion of the hub are integrally formed, and an upper flange which has the same configuration of the lower flange is bonded at an upper end of the hub. The magnetic tape is wound on a peripheral surface of the hub.
As shown in FIGS. 5A and 5B, a reel gear 108 having a ring configuration in a plane view is carved (provided) on a central portion of a lower surface of a reel 104 (a lower flange portion 106) which appears from an opening hole 102 drilled (provided) on a lower surface of a case 100. The reel 104 is driven to rotate by mashing a driving gear 110 provided at a rotating shaft of the drive device with the reel gear 108. That is, rotation power is transmitted to rotate the reel 104 by the reel gear 108 having a substantially saw tooth configuration and the driving gear 110 having a substantially saw tooth configuration being meshed each other.
However, when the reel 104 is rotated in a direction indicated by an arrow R in FIG. 5B by meshing the reel gear 108 having substantially saw tooth configuration and the driving gear 110 having substantially saw tooth configuration being meshed each other, there may be a case in which the driving gear 110 pushes the reel gear 108 upwardly thereby a small displacement (clearance) S is generated in a meshed portion between the reel gear 108 and the driving gear 110. When such displacement (clearance) S is generated, so-called “swelling” by which the lower flange 106 swings (moves) upwardly and downwardly is generated. This “swelling” may affect unpreferable influence on feeding out and rewinding of a magnetic tape T. Further, because a substantially central position in a height direction in a side view (a position indicated by an imaginary line (a two dotted line) K in FIG. 5B) at this meshed portion is set as a reference portion (a reference surface) in the height direction of the reel 104 with respect to the drive device, there is a problem in which a position of the reference portion (the reference surface) becomes unstable and therefore accurate positioning becomes difficult in a case in which displacement (clearance) S is generated in meshing between the reel gear 108 and the driving gear 110.